Friday, February 18, 2011

[Stylized photo of the AAAS Annual Meeting registration area at the Washington Convention Center in Washington, D.C.]

Looking at tofu: That's how Eric Betzig of the Howard Hughes Medial Institute (HHMI) in Ashburn, Va. described a close-up view of an eye. Trying to see deep tissue in an eye or even in a brain, he said, is like trying to see "a field of stars hidden behind a cloud." It's hard.

But one technique, used by every major telescope on Earth, according to Betzig, could help doctors and biologists see deep tissues in the brain. It's called adaptive optics and it's what astronomers use to bring their cosmic snapshots into focus.Betzig spoke in an early-morning session at the American Association for the Advancement of Science (AAAS) annual meeting today at the Washington Convention Center in Washington, D.C.

When looking at stars and other celestial beasts, the vision of Earth-based telescopes is distorted by the atmosphere. To correct for this, astronomers shine a laser, like this one at NASA's Goddard Space Flight Center, up into the atmosphere, creating an artificial star.

The astronomers measure the distortion affecting this artificial star and apply a correction to it. They then apply the same correction to the actual stars being measured, allowing them to capture the stars in high resolution -- a technique called adaptive optics.

Without the technique, even the biggest and best telescope would have a resolution no better than a 50cm (about 20 inches) diameter telescope.

[Eric Betzig]

The same resolution problem is encountered by scientists using microscopy to probe deep tissues in the brain. Taking inspiration from astronomers' creation of an artificial "guide" star, Betzig and his colleagues decided to use a fluorescent bead inserted into tissue as a sort of biological guide star.

"Can we do this in living mice?" they asked. In their brains? To try it out, the researchers injected fluorescent beads into mice pups' brains before they were born using a dental drill. (Don't worry! They used anesthesia.) Once the pups were born, they were able to image the deep brain tissue.

Correcting a fuzzy image using the implanted fluorescent beads takes about 10 to 25 seconds, Betzig said. And while telescopes have to correct themselves against their guide stars hundreds of times each second, the microscopy adaptive optics requires correction only once an hour.

The researchers watched the neural activity in the brains of the mice as they watched T.V. Using adaptive optics with microscopy, Betzig said, gave them a chance to look at the functions of the brain with a very clear picture.

When asked by an audience member where the technique could be used in the future, Betzig said an area that might be "really fun" is acoustics. "Like sonograms," he said. He remembered seeing sonograms of his baby before it was born 9 months ago and thinking, "That looks pretty crappy. Why can't we do better?"